The present invention relates to optical fiber technology and, more particularly, to optical devices useful in fiber optic networks, such as optical switches and optical attenuators.
Complex electronic systems such as required for ground and space control, command, radio/data transmission, sensor rays, telecommunications and networks, require high performance switches for switching matrices. Heretofore, most conventional electrical or electrical mechanical switching matrices have had shortcomings of large thermal effects and heat problems, large size, weight, cost in power consumption, narrow operational bandwidth and susceptibility to electromagnetic interference, electromagnetic pulses or RF interference.
Thus many communications and control systems have migrated to fiber optic or electro-optical systems to avoid many of these problems, such as electromagnetic interference, electromagnetic pulse, or RF interference immunity, and to reduce the size, weight and cost of elements in these systems. However, current fiber optic or electro-optic switches still have various disadvantages. For example, commercially available fiber optic switches are 1.times.2 or are 2.times.2 configurations. However, these switches have certain problems including, large physical size, high cost, poor reliability due to the movement of mechanical parts within the switch. Furthermore, these types of switches make it difficult to construct a micro-miniature switching matrix because the switches require mechanical mountings in various fiber optic interconnections and splicings. Furthermore, these optical switches have slow switching speeds and consume large amounts of power to move the mechanical parts which, in turn, results in undesirably large heat generation.
Another example is a deflection type switch which has liquid crystal, electro-optic lithium niobate (LiNbO.sub.3), or acoustic optic crystal. These do not have the disadvantages of the aforementioned opto-mechanical fiber optic switches. Furthermore, these switches can operate at high (picosecond) switching speeds. However, these switches require complex fabrication processes which result in high cost and difficulty in manufacturing a switching array. Furthermore, performance shortcomings include high insertion loss and poor immunity from crosstalk.
Another type of switch, the liquid crystal shutter switch, avoids many of the problems of electro-optical switch and the deflection type switch. This type of switch can easily be combined to form a switching matrix or switch array. However, a disadvantage of this type of switch is that it is sensitive to the polarization of the incoming light signal and may have up to 3 dB insertion loss.
The present invention solves or substantially mitigates the problems of the liquid crystal shutter switch while retaining its many advantages.